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Synthesis and EPR Studies of 2′‐Deoxyuridines with Alkynyl, Rodlike Linkages
Author(s) -
Sniady Adam,
Sevilla Michael D.,
Meneni Srinivasarao,
Lis Tadeusz,
Szafert Slawomir,
Khanduri Deepthi,
Finke John M.,
Dembinski Roman
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900481
Subject(s) - chemistry , unpaired electron , sonogashira coupling , cycloisomerization , electron paramagnetic resonance , delocalized electron , deoxyuridine , dimer , crystallography , stereochemistry , photochemistry , medicinal chemistry , catalysis , palladium , radical , nuclear magnetic resonance , dna , organic chemistry , physics , biochemistry
Sonogashira coupling of diacetyl 5‐ethynyl‐2′‐deoxyuridine with diacetyl 5‐iodo‐2′‐deoxyuridine gave the acylated ethynediyl‐linked 2′‐deoxyuridine dimer ( 3 b ; 63 %), which was deprotected with ammonia/methanol to give ethynediyl‐linked 2′‐deoxyuridines ( 3 a ; 79 %). Treatment of 5‐ethynyl‐2′‐deoxyuridine ( 1 a ) with 5‐iodo‐2′‐deoxyuridine gave the furopyrimidine linked to 2′‐deoxyuridine (78 %). Catalytic oxidative coupling of 1 a (O 2 , CuI, Pd/C, N , N ‐dimethylformamide) gave butadiynediyl‐linked 2′‐deoxyuridines ( 4 ; 84 %). Double Sonogashira coupling of 5‐iodo‐2′‐deoxyuridine with 1,4‐diethynylbenzene gave 1,4‐phenylenediethynediyl‐bridged 2′‐deoxyuridines ( 5 ; 83 %). Cu‐catalyzed cycloisomerization of dimers 4 and 5 gave their furopyrimidine derivatives. One‐electron addition to 1 a , 3 a , and 4 gave the anion radical, the EPR spectra of which showed that the unpaired electron is largely localized at C6 of one uracil ring (17 G doublet) at 77 K. The EPR spectra of the one‐electron‐oxidized derivatives of ethynediyl‐ and butadiynediyl‐linked uridines 3 a and 4 at 77 K showed that the unpaired electron is delocalized over both rings. Therefore, structures 3 a and 4 provide an efficient electronic link for hole conduction between the uracil rings. However, for the excess electron, an activation barrier prevents coupling to both rings. These dimeric structures could provide a gate that would separate hole transfer from electron transport between strands in DNA systems. In the crystal structure of acylated dimer 3 b , the bases were found in the anti position relative to each other across the ethynyl link, and similar anti conformation was preserved in the derived furopyrimidine–deoxyuridine dinucleoside.